I mean, if you think about all the motherboard does, and how many layers the PCB has to support all the features such that for a vast majority of users, the only things you need besides the motherboard is a CPU, some RAM, storage (either in M.2 or SATA) and maybe a dGPU, it's wild that it is often the cheapest item in the PC.

Well to be fair processors, ram and modern storage are lithography required to make parts. Not sure how much lithography the chipset requires.